This seems to be a problem that many people have, and only a small minority know how to fix. Symptoms include: not being able to connect to certain people, very long searches in matchmaking, consistent lag problems, and finally the tell-tale sign; a "Strict" or "Moderate" NAT when running the connection test. However, even with an "Open" NAT, you may have problems.

This is something every 360 owner should do, even if you don't believe you have any problems. You may find yourself surprised when you all-of-the-sudden are able to find games twice as fast!

Finding Out Your Router's Gateway and Subnet Mask

Note: Apostrophe marks and quotations are for differentiating between what you are supposed to type or what you should see, and what is simply part of the directions. You do NOT type those into the fields, you just type in what is in-between them

Go on any PC that is connected to the same router as your Xbox 360

Hit the 'Start' button

Click on 'Run' (alternatively, you can just press WindowKey-R on your keyboard)

In the 'Run' window, type-in 'cmd'

In the command prompt, type in 'ipconfig/all'

A large list of numbers should pop-up.

Find where it says "Default Gateway" and write it down somewhere for later. Do the same for the "Subnet Mask"

Setting a Static IP for Xbox 360

Note: if you plan on using "Alternative: Port Triggering" instead, then skip this step. You must have an IP assigned automatically by your router's DHCP server to use port triggering. Port forwarding and DMZ require you to have a static IP however.

Go onto your Xbox 360

Go to the "My Xbox" tab (post-NXE update).

Go to "System Settings"

Go to "Network Settings

Go to "Configure Network"

On the "Basic Settings" tab, click on the first box.

It should prompt you to choose between "Automatic" and "Manual". Choose "Manual"

Go ahead and enter the "Subnet Mask" IP you got from the last section into where it says "Subnet Mask" on your 360 (it's usually 255.255.255.0)

Also enter the "Default Gateway" you got from the last section into where it says "Gateway" on your 360

Okay now we're going to enter a static IP. This is important: you need to choose an IP that has all the same numbers as the "Default Gateway", except for the numbers after the last dot. If you don't do this, then the 360 won't be able to connect. Also, the number must be less than 254.

Now, you are likely to have what is called a "DHCP" server on your router that automatically assigns IPs to devices that connect to it. This DHCP server likely takes IPs from 0-149, so I suggest choosing something between 150 and 254 to be safe. Be sure to write down the static IP you just set for later!

Accessing Your Router's Configuration Page

Take the default gateway you obtained in the first section and type it into an internet browser on the address bar (Internet Explorer, Mozilla Firefox, etc)

You should be prompted for a username and password

Refer to this nice little guide I found here for what your default username and password are. You can use the key combination Ctrl-F to quickly search the page for your router.

If your router is not listed, then try using the username and password of a router made by the same company. If you have manually changed the username and password before, then just enter that instead

Forwarding Ports

Alright, now you are going to have to do a little navigation by yourself. As you can probably guess, each router's configuration page is different. These are some of the keywords you are looking for "Applications & Gaming", "Port Forwarding", and "NAT". You may have to enter some sort of 'expert' or 'advanced' mode to see these things, so don't be afraid to do so.

Eventually, you should come across something that allows you to enter different port numbers/ranges and an IP address

For example, here is how it looks on my Linksys router:

If you are absolutely stuck trying to find it, then you may want to refer to portforward.com's guide. Their guides are a little vague, but they do include pictures to show you where to navigate to. Simply choose your router from their list, and you should be given a guide on how to access the port forwarding page on your specific router type.

Once you find this field, you'll need to enter the following ports:

TCP 80

UDP 88

UDP 3074

TCP 3074

UDP 53

TCP 53

If your router asks you for a "range" instead of just a single number (like mine does in the picture above), then just enter that same number in both fields.

Very important! Assign each of these ports to the static IP you gave your Xbox 360 in this section

Alternative: DMZ

Instead of forwarding only certain ports, you may want to choose the option of DMZ instead. Try finding this feature somewhere on your router. If you look at the picture of my configuration page above, you can clearly see the DMZ option as one of the links towards the top of the page.

DMZ will essentially forward all the ports, instead of just the few that you specify. This may be leave a PC vulnerable, but this shouldn't be a problem for an Xbox 360. Simply take the static IP you gave your 360 in this section and enter it into the DMZ field, like I did here:

Not only is this method a bit simpler, but it may actually help more, since you're essentially forwarding every port possible.

Alternative: Port Triggering

Note: you must use DHCP with port triggering! Make sure the DHCP server on your router is enabled, and your network settings on your Xbox 360 are all set to 'Automatic'.

Port triggering has it's advantages and disadvantages, and much of the time port forwarding or DMZ may be the better solutions. However, in some cases, even the DMZ method will still leave you with a rather agitating "Your NAT is moderate" message on Xbox Live. This is true in my personal experience as well. If this is the case, you may want to make the quick and effortless switch to port triggering instead. Port triggering may also may work better for when you have two Xbox 360s on the same network that are trying to play together.

Closing Section

Any questions or problems? Feel free to ask them in this thread, and myself or anyone else familiar with this sort of thing will be glad to answer them.

Port forwarding is no good when you have two different XBOX consoles on the same router cause one always remains as a strict NAT while the other is open. Then you have to do 'port triggering' and sometimes disable DMZ. Also, activating UPNP can allow two XBOX consoles to be open NAT.

It's all fun and games till you want 2 XBOXs on the same router with an open NAT.

I haven't done anything to it yet. I just thought that I post the error message first just in-case it's something as simple changing the setting without having to go through all that. I'm not of a tech guy so I didnt really want to have to do it unless I really have to, just in-case I made it worst.